Coffee is one of the world's top three beverages and ranks second
only to oil as a traded commodity. According to the International
Coffee Organization (ICO), global coffee consumption in 2022 was
approximately
6.483
million tons.
However, coffee beans do not entirely convert into coffee. Based on
ICO statistics, one ton of coffee beans generates
650 kg of coffee
grounds, resulting in an estimated
4 million tons of
coffee grounds in 2022.
Despite such a massive amount of coffee grounds waste, there is no
effective recycling method for it. The primary methods of coffee
ground disposal remain incineration, landfill, or reuse as animal
feed and fertilizer.
These approaches are not only economically inefficient but can also
lead to the breakdown of coffee grounds into environmentally harmful
substances. Moreover, there is a lack of practical, commercially
valuable, and eco-friendly recycling methods.
Thus, finding a solution to recycle coffee ground waste is an urgent
challenge!
How to Recycle?
Pseudomonas putida CBB5 is capable of naturally metabolizing
caffeine, a major component in coffee grounds, and among its various
methylxanthine metabolites, 7-methylxanthine (7-MX) has caught our
attention.
7-MX is a novel and promising drug for the treatment of myopia.
Long-term oral 7-MX administration can slow down the progression of
myopia. Existing studies have proven that 7-MX it has no toxic side
effects and is safe for use.
Therefore, transferring the caffeine-metabolizing enzymes from
Pseudomonas putida CBB5 into E. coli to produce 7-MX may open a new
avenue for coffee ground disposal and simultaneously produce a
product with a high economic value.
How to Achieve This?
By conducting directed evolution on the key genes NdmA and NdmB, we
can develop a more efficient method to achieve the one-step
conversion of caffeine to 7-MX.
A 7-MX whole-cell biosensor can be constructed as a high-throughput
screening tool to identify and select strains that can efficiently
produce 7-MX.
Finally, reaction conditions will be explored to successfully convert caffeine, ultimately achieving the
recycling of coffee grounds.
